Answer:
A and B
Step-by-step explanation:
Terms are the sets of numbers, excluding the signs. So 15x^4 is one term, so is 12, or 8x^3, or 5x.
A has exactly 4 terms because 15x^4 is a term, and 9x^2, 5x, and 12 are all terms.
B has exactly 2 terms because 12y^3, 8y^2, 4y, and 20 are terms, and those are 4 terms.
C does not, however. 18 is a term, and so is 4^3 (which is technically 64). However, -5n and 3n are not two terms, but just one. This is because they can be combined, and are similar terms. Thus, C's expression is really just 18-2n+4^3. 18 is a term, -2n is a term, and 4^3 is a term. C only has 3 terms.
D does not have 4 terms, just 2, 4x^3 and 12x.
